ASTRO-ENTOMOLOGY? ANT-LIKE SPACE STRUCTURE PREVIEWS DEATH OF OUR SUN

From
ground-based telescopes, the so-called "ant nebula"
(Menzel 3, or Mz 3) resembles the head and thorax
of a garden-variety ant. This dramatic NASA/ESA
Hubble Space Telescope image, showing 10 times
more detail, reveals the "ant's" body as a pair
of fiery lobes protruding from a dying, Sun-like
star.

The Hubble images
directly challenge old ideas about the last stages
in the lives of stars. By observing Sun-like stars
as they approach their deaths, the Hubble Heritage
image of Mz 3 -- along with pictures of other
planetary nebulae -- shows that our Sun's fate
probably will be more interesting, complex, and
striking than astronomers imagined just a few
years ago.

Though
approaching the violence of an explosion, the
ejection of gas from the dying star at the center
of Mz 3 has intriguing symmetrical patterns unlike
the chaotic patterns expected from an ordinary
explosion. Scientists using Hubble would like
to understand how a spherical star can produce
such prominent, non-spherical symmetries in the
gas that it ejects.

One
possibility is that the central star of Mz 3 has
a closely orbiting companion that exerts strong
gravitational tidal forces, which shape the outflowing
gas. For this to work, the orbiting companion
star would have to be close to the dying star,
about the distance of the Earth from the Sun.
At that distance the orbiting companion star wouldn't
be far outside the hugely bloated hulk of the
dying star. It's even possible that the dying
star has consumed its companion, which now orbits
inside of it, much like the duck in the wolf's
belly in the story "Peter and the Wolf." An animation
shows how this might work.

A second possibility
is that, as the dying star spins, its strong magnetic
fields are wound up into complex shapes like spaghetti
in an eggbeater. Charged winds moving at speeds
up to 1000 kilometers per second from the star,
much like those in our sun's solar wind but millions
of times denser, are able to follow the twisted
field lines on their way out into space. These
dense winds can be rendered visible by ultraviolet
light from the hot central star or from highly
supersonic collisions with the ambient gas that
excite the material into florescence.

No other planetary
nebula observed by Hubble resembles Mz 3 very
closely. M2-9 comes close, but the outflow speeds
in Mz 3 are up to 10 times larger than those of
M2-9 (STScI
PR97-38). Interestingly, the very massive,
young star, Eta Carinae (STScI
PR96-23), shows a very similar outflow pattern.

Astronomers Bruce Balick (University
of Washington) and Vincent Icke (Leiden University)
used Hubble to observe this planetary nebula,
Mz 3, in July 1997 with the Wide Field Planetary
Camera 2. One year later, astronomers Raghvendra
Sahai and John Trauger of the Jet Propulsion Lab
in California snapped pictures of Mz 3 using slightly
different filters. This intriguing image, which
is a composite of several filters from each of
the two datasets, was created by the Hubble Heritage
Team.